U.S. patent application number 11/472879 was filed with the patent office on 2007-12-27 for linear solid state illuminator.
Invention is credited to Jeffrey B. Sampsell.
Application Number | 20070297191 11/472879 |
Document ID | / |
Family ID | 38683494 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070297191 |
Kind Code |
A1 |
Sampsell; Jeffrey B. |
December 27, 2007 |
Linear solid state illuminator
Abstract
An illuminator for a display is provided that includes a light
guide plate to substantially cover a viewable portion of the
display, and a thin film light-emitting source. Light from the thin
film light-emitting source is directed into an edge of the light
guide plate to provide light for the viewable portion of the
display.
Inventors: |
Sampsell; Jeffrey B.; (San
Jose, CA) |
Correspondence
Address: |
KNOBBE, MARTENS, OLSON & BEAR, LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
38683494 |
Appl. No.: |
11/472879 |
Filed: |
June 21, 2006 |
Current U.S.
Class: |
362/602 |
Current CPC
Class: |
G02B 6/0073 20130101;
G02B 6/0018 20130101; G02B 6/0036 20130101; G02B 6/0046
20130101 |
Class at
Publication: |
362/602 |
International
Class: |
F21V 7/04 20060101
F21V007/04 |
Claims
1. An illuminator for a display comprising: a light guide plate to
substantially cover a viewable portion of the display; and a thin
film light-emitting source, wherein light from the thin film
light-emitting source is directed into an edge of the light guide
plate to provide light for the viewable portion of the display.
2. The illuminator of claim 1, wherein the thin film light-emitting
source is bonded directly to the edge of the light guide plate.
3. The illuminator of claim 1, wherein the thin film light-emitting
source comprises an organic light-emitting diode (OLED).
4. The illuminator of claim 1, wherein the thin film light-emitting
source comprises an electroluminescent (EL) thin film light
source.
5. The illuminator of claim 3, wherein the organic light-emitting
diode (OLED) consists of a single pixel.
6. The illuminator of claim 5, wherein a first dimension of the
pixel is substantially equal to a thickness of the light guide
plate and a second dimension of the pixel is substantially equal to
a length of the edge of the light guide plate.
7. The illuminator of claim 5, wherein the pixel comprises a white
pixel.
8. The illuminator of claim 7, wherein the white pixel is created
by a plurality of separate wavelength emissions that are matched to
a plurality of specific reflectivities of subpixels that make up
each pixel of a color display.
9. The illuminator of claim 5, wherein the pixel comprises a pixel
having emissions substantially centered around a specific
wavelength matched to a specific reflectivity of a monochrome
display.
10. The illuminator of claim 5, the pixel having emissions
substantially peaking around two specific wavelengths that are
matched to a reflectivity of a bichrome display.
11. The illuminator of claim 3, further comprising an
angle-matching component to direct the light from the organic
light-emitting diode (OLED) into the edge of the light guide
plate.
12. The illuminator of claim 11, wherein at least a portion of the
angle-matching component has a substantially parabolic or
elliptical shape for collimating the light from the organic
light-emitting diode (OLED) into the edge of the light guide
plate.
13. The illuminator of claim 12, wherein the angle-matching
component is molded directly into the light guide plate.
14. The illuminator of claim 13, wherein the organic light-emitting
diode (OLED) is bonded directly to the surface of the light guide
plate.
15. The illuminator of claim 1, wherein the light guide plate
comprises a plurality of facets molded into the surface of the
light guide plate so that the light from the thin film
light-emitting source exits from the light guide plate in a
substantially uniform fashion over the viewable portion of the
display.
16. The illuminator of claim 1, wherein a thickness of the light
guide plate is tapered along one edge of the light guide plate.
17. The illuminator of claim 1, wherein the illuminator is
implemented within a front lighting system or a back lighting
system of a display.
18. A display device comprising the illuminator of claim 1.
19. The display device of claim 18, wherein the display device
comprises an interferometric modulator display.
20. The display device of claim 19, further comprising: a processor
that is in electrical communication with the interferometric
modulator display, the processor being configured to process image
data; and a memory device in electrical communication with the
processor.
21. The display device of claim 20, further comprising: a first
controller configured to send at least one signal to the
interferometric modulator display; and a second controller
configured to send at least a portion of the image data to the
first controller.
22. The display device of claim 20, further comprising an image
source module configured to send the image data to the
processor.
23. The display device of claim 22, wherein the image source module
comprises at least one of a receiver, transceiver, and
transmitter.
24. The display device of claim 20, further comprising an input
device configured to receive input data and to communicate the
input data to the processor.
25. An illuminator for a display comprising: a light guide means
for substantially covering a viewable portion of the display; and
thin film means for emitting light, wherein light from the thin
film light-emitting means is directed into an edge of the light
guide means for providing light to the viewable portion of the
display.
26. The illuminator of claim 25, wherein the thin film
light-emitting means is bonded directly to the edge of the light
guide means.
27. The illuminator of claim 25, wherein the thin film
light-emitting means comprises an organic light-emitting means.
28. The illuminator of claim 27, wherein the organic light-emitting
means consists of a single pixel means.
29. The illuminator of claim 28, wherein a first dimension of the
pixel means is substantially equal to a thickness of the light
guide means and a second dimension of the pixel means is
substantially equal to a length of the edge of the light guide
means.
30. The illuminator of claim 28, wherein the pixel means comprises
a white pixel means.
31. The illuminator of claim 27, further comprising an
angle-matching component means for directing the light from the
organic light-emitting means into the edge of the light guide
means.
32. The illuminator of claim 31, wherein at least a portion of the
angle-matching component means has a substantially parabolic or
elliptical shape for collimating the light from the organic
light-emitting means into the edge of the light guide means.
33. The illuminator of claim 32, wherein the angle-matching
component means is molded directly into the light guide means.
34. The illuminator of claim 33, wherein the organic light-emitting
means is bonded directly to the surface of the light guide
means.
35. The illuminator of claim 25, wherein the light guide means
comprises a plurality of facet means molded into the surface of the
light guide means so that the light from the thin film
light-emitting means exits from the light guide means in a
substantially uniform fashion over the viewable portion of the
display.
36. The illuminator of claim 25, wherein a thickness of the light
guide means is tapered along one edge of the light guide means.
37. A method of manufacturing an illuminator for a display, the
method comprising: providing a light guide plate, the light guide
plate to substantially cover a viewable portion of the display; and
coupling a thin film light-emitting source to the light guide
plate, wherein light from the thin film light-emitting source is
directed into an edge of the light guide plate to provide light to
the viewable portion of the display.
38. The method of claim 37, wherein the thin film light-emitting
source comprises an organic light-emitting diode (OLED).
39. The method of claim 37, wherein coupling a thin film
light-emitting source to the light guide plate comprises bonding
the thin film light-emitting source directly to an edge of the
light guide plate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to display devices,
and more particularly to an illuminator for display devices.
BACKGROUND OF THE INVENTION
[0002] Non-emissive display devices (referred to herein as "display
devices") (e.g., STN LCD, iMoD, or TFT LCD) typically include a
front lighting or a back lighting system to increase visibility and
display quality of images (e.g., text, line art, graphical images,
and the like) shown on the display devices. FIGS. 1A-1D illustrate
components of a conventional front lighting system 100 for a
reflective display device. Referring first to FIGS. 1A-1B, the
front lighting system 100 includes a light emitting diode (LED)
102, an angle-matching component 104, and an (injection molded)
light bar 106. The LED 102 is placed at one end of the light bar
106 to direct light into the light bar 106, and the angle-matching
component 104 is placed between the LED 102 and the light bar 106
to maximize the amount of light captured by the light bar 106. The
light directed in to the light bar 106 is generally confined within
the light bar through total internal reflection (TIR) at the
air/light bar interface surrounding the light bar 106. The light
bar 106 typically includes a plurality of facets 108 (or features)
molded into a face of the light bar that disrupts the total
internal reflection of the light. The facets 108 are typically
precisely designed and spaced to ensure that light exits from the
light bar 106 in a uniform fashion along the length of the light
bar.
[0003] Referring to FIGS. 1C-1D, the front lighting system 100
further includes a reflector 110 and a light guide plate 112. The
light guide plate 112 is bonded to the light bar 106 and
substantially covers a viewable portion of a display device 114.
The reflector 110 directs the light exiting from the light bar 106
towards the light guide plate 112, which light is then, once again,
generally totally internally reflected within the light guide plate
112. The light guide plate 112 typically includes a plurality of
facets (not shown) that are molded onto the surface 116 of the
light guide plate 112. These facets disrupt the total internal
reflection of the light within the light guide plate 112 and direct
light uniformly onto the display device 114.
[0004] In high volume manufacturing of display devices, the
cumulative costs associated with the individual components of a
conventional front lighting system can be substantial. Accordingly,
what is needed is a front lighting system that includes fewer
components than conventional front lighting systems. The present
invention addresses such a need.
BRIEF SUMMARY OF THE INVENTION
[0005] In general, in one aspect, this specification describes an
illuminator for a display that includes a light guide plate to
substantially cover a viewable portion of the display, and a thin
film light-emitting source. Light from the thin film light-emitting
source is directed into an edge of the light guide plate to provide
light for the viewable portion of the display.
[0006] Particular implementations can include one or more of the
following features. The thin film light-emitting source can be
bonded directly to the edge of the light guide plate. The thin film
light-emitting source can comprise an organic light-emitting diode
(OLED) or an electroluminescent (EL) thin film light source. The
organic light-emitting diode (OLED) can consist of a single pixel.
A first dimension of the pixel can be substantially equal to a
thickness of the light guide plate and a second dimension of the
pixel can be substantially equal to a length of the edge of the
light guide plate. The pixel can comprise a white pixel that is,
e.g., created by a plurality of separate wavelength emissions that
are matched to a plurality of specific reflectivities of subpixels
that make up each pixel of a color display. The pixel can comprise
a pixel having emissions substantially centered around a specific
wavelength matched to a specific reflectivity of a monochrome
display. The pixel can have emissions that substantially peak
around two specific wavelengths that are matched to a reflectivity
of a bichrome display.
[0007] The illuminator can further include an angle-matching
component to direct the light from the organic light-emitting diode
(OLED) into the edge of the light guide plate. At least a portion
of the angle-matching component can have a substantially parabolic
or elliptical shape for collimating the light from the organic
light-emitting diode (OLED) into the edge of the light guide plate.
The angle-matching component can be molded directly into the light
guide plate. The organic light-emitting diode (OLED) can be bonded
directly to the surface of the light guide plate. The light guide
plate can comprise a plurality of facets molded into the surface of
the light guide plate so that the light from the thin film
light-emitting source exits from the light guide plate in a
substantially uniform fashion over the viewable portion of the
display. A thickness of the light guide plate can be tapered along
one edge of the light guide plate. The illuminator can be
implemented within a front lighting system or a back lighting
system of a display.
[0008] In general, in another aspect, this specification describes
a display device comprising the illuminator, discussed above. The
display device can comprise an interferometric modulator display.
The display device can further include a processor that is in
electrical communication with the interferometric modulator display
and a memory device in electrical communication with the processor.
The processor can be configured to process image data. The display
device can further include a first controller configured to send at
least one signal to the interferometric modulator display, and a
second controller configured to send at least a portion of the
image data to the first controller. The display device can further
include an image source module configured to send the image data to
the processor. The image source module can comprise at least one of
a receiver, transceiver, and transmitter. The display device can
further include an input device configured to receive input data
and to communicate the input data to the processor.
[0009] In general, in another aspect, this specification describes
an illuminator for a display comprising a light guide means for
substantially covering a viewable portion of the display; and thin
film means for emitting light, in which light from the thin film
light-emitting means is directed into an edge of the light guide
means for providing light to the viewable portion of the
display.
[0010] In general, in another aspect, this specification describes
a method of manufacturing an illuminator for a display. The method
includes providing a light guide plate, in which the light guide
plate substantially covers a viewable portion of the display. The
method further includes coupling a thin film light-emitting source
to the light guide plate, in which light from the thin film
light-emitting source is directed into an edge of the light guide
plate to provide light to the viewable portion of the display.
[0011] Implementations may provide one or more of the following
advantages. An improved front lighting system for a display device
that includes a reduced number of components relative to
conventional front lighting systems. In one implementation, a front
lighting system is provided that consists of as few as two
components unlike a conventional front lighting system that
typically consists of five or six components. In one
implementation, a front lighting system is described that includes
an organic light-emitting diode (OLED) as a light source. A thin
film light-emitting source (e.g., an organic light-emitting diode
(OLED)) typically costs the same as a conventional LED and,
therefore, a substantial costs saving can be realized in high
volume manufacturing of display devices that include a front
lighting system such as those described herein. A light source
including an organic light-emitting diode (OLED) can be fabricated
through manufacturing methods more akin to polymer manufacturing
traditions than to semiconductor manufacturing traditions.
[0012] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
and advantages will be apparent from the description and drawings,
and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A-1D illustrate a conventional front lighting system
for a display.
[0014] FIGS. 2A-2B illustrate a front lighting system.
[0015] FIG. 3 is a flowchart of a process for implementing a front
lighting system.
[0016] FIG. 4 illustrates an organic light emitting diode
(OLED).
[0017] FIG. 5 illustrates a cross section of the organic light
emitting diode (OLED) of FIG. 4.
[0018] FIGS. 6-8 respectively illustrate a front lighting
system.
[0019] FIG. 9 is an isometric view depicting a portion of one
embodiment of an interferometric modulator display that can
incorporate a front lighting system in accordance with one
implementation of the present invention.
[0020] FIG. 10 is a system block diagram illustrating one
embodiment of an electronic device incorporating a 3.times.3
interferometric modulator display.
[0021] FIG. 11 is a diagram of movable mirror position versus
applied voltage for one exemplary embodiment of an interferometric
modulator of FIG. 9.
[0022] FIG. 12 is an illustration of a set of row and colurn
voltages that may be used to drive an interferometric modulator
display.
[0023] FIGS. 13A-13B illustrate one exemplary timing diagram for
row and column signals that may be used to write a frame of display
data to the 3.times.3 interferometric modulator display of FIG.
10.
[0024] FIGS. 14A-14B are system block diagrams illustrating an
embodiment of a visual display device comprising a plurality of
interferometric modulators.
[0025] FIG. 15A is a cross section of an interferometric modulator
of FIG. 9. FIGS. 15B-15E are alternative embodiments of an
interferometric modulator.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The following detailed description is directed to certain
specific embodiments of the invention. However, the invention can
be embodied in a multitude of different ways. In this description,
reference is made to the drawings wherein like parts are designated
with like numerals throughout. As will be apparent from the
following description, the embodiments of a front lighting system
described herein may be implemented in any device that is
configured to display an image, whether in motion (e.g., video) or
stationary (e.g., still image), and whether textual or pictorial.
More particularly, it is contemplated that the embodiments may be
implemented in or associated with a variety of electronic devices
such as, but not limited to, mobile telephones, wireless devices,
personal data assistants (PDAs), hand-held or portable computers,
GPS receivers/navigators, cameras, MP3 players, camcorders, game
consoles, wrist watches, clocks, calculators, television monitors,
flat panel displays, computer monitors, auto displays (e.g.,
odometer display, etc.), cockpit controls and/or displays, display
of camera views (e.g., display of a rear view camera in a vehicle),
electronic photographs, electronic billboards or signs, projectors,
architectural structures, packaging, and aesthetic structures
(e.g., display of images on a piece of jewelry).
Micro-electromechanical systems (MEMS) devices of similar structure
to those described herein can also be used in non-display
applications such as in electronic switching devices.
[0027] As discussed above, reflective display devices typically
implement a front lighting system that provides light for viewing
images, for example, in the dark. Conventional front lighting
systems, however, include a number of components, the costs of
which can be substantial with respect to high volume manufacturing
of display devices. Accordingly, this specification describes an
improved front lighting system for a display device that includes a
reduced number of components relative to conventional front
lighting systems. In one embodiment, an illuminator for a display
is provided that includes a light guide plate to substantially
cover a viewable portion of the display, and a thin film
light-emitting source. Light from the thin film light-emitting
source is directed into an edge of the light guide plate to provide
light for the viewable portion of the display.
[0028] FIGS. 2A-2B respectively illustrate a side view and a
perspective view of a front lighting system 200 in accordance with
one embodiment. The front lighting system 200 includes a light
source 202 and a light guide plate 204. In one embodiment, the
light source 202 is bonded directly to an edge of the light guide
plate 204. In one embodiment, the front lighting system further
includes a reflector (not shown) to direct light exiting from the
light source 202 towards the light guide plate 204. The light guide
plate 204 is configured to substantially cover a viewable portion
of a display device (e.g., display device 206), and provide light
for the viewable portion of the display device. In one embodiment,
the light source 202 comprises a thin film light-emitting source.
The thin film light-emitting source can be an organic
light-emitting diode (OLED) in which the emissive layer is an
organic compound. In general, the thin film light-emitting source
can be any type of thin film light-emitting source operable to
produce light, such as for example, both small and large molecule
OLEDs or fluorescent OLEDs. Alternatively, an electroluminescent
(EL) thin film light source can be used. In one embodiment, the EL
material is enclosed between two electrodes, in which at least one
electrode is transparent to allow the escape of the produced light.
Glass coated with indium oxide or indium tin oxide (ITO) is
commonly used as the front (transparent) electrode while the back
electrode is or is coated with reflective metal.
[0029] In one embodiment, the thin film light-emitting source
(e.g., an organic light-emitting diode (OLED)) consists of a single
pixel having one dimension that is substantially the same as the
thickness of the light guide plate 204 and one dimension that is
substantially the same as the length of one edge of the light guide
plate 204. The pixel can be a white pixel (or any other
color--e.g., a pixel having emissions centered around a specific
wavelength matched to the specific reflectivity of a monochrome
display). In one implementation, the pixel has emissions that
substantially peaks around two specific wavelengths that are
matched to a reflectivity of a bichrome display. The white pixel
can be created by three (or more) separate wavelength emissions
that are matched to three (or more) specific reflectivities of the
three (or more) subpixels that (in one implementation) make up each
pixel of a color display. Also, a white light can be made of two
complementary colors, e.g., blue and yellow. In operation, light
from the light source 202 is directed into an edge of the light
guide plate 204. In one embodiment, the light guide plate 204
includes a plurality of facets (not shown) that are molded onto the
surface 208 of the light guide plate 204. The facets direct light
uniformly onto the display device 206.
[0030] Accordingly, in one embodiment, the front lighting system
200 consists of as few as two components unlike a conventional
front lighting system that typically consists of five or six
components. A thin film light-emitting source (e.g., an organic
light-emitting diode (OLED)) typically costs the same as a
conventional LED and, therefore, a substantial costs saving can be
realized in high volume manufacturing of display devices that
include a front lighting system such as those described herein.
[0031] FIG. 3 illustrates a process 300 of implementing a front
lighting system (e.g., front lighting system 200) in accordance
with one embodiment. The process 300 begins with providing a light
guide plate (e.g., light guide plate 204) (step 302). In general,
the light guide plate is an optical waveguide through which light
can travel. In one embodiment, the light guide plate includes a
plurality of facets (or features) that uniformly direct light
towards a display device (e.g., a liquid crystal display (LCD)) to
provide light for the display device. A thin film light-emitting
source is coupled to the light guide plate (step 304). In one
embodiment, the thin film light-emitting source is bonded directly
to an edge of the light guide plate. In another embodiment, the
thin film light-emitting source is bonded directly to the surface
of the light guide plate (as discussed in greater detail below with
respect to FIG. 7). As discussed above, the thin film
light-emitting source can be any type of thin film light-emitting
source operable to produce light. In one embodiment, the thin film
light-emitting source is an organic light-emitting diode (OLED).
Alternatively, the thin film light-emitting source can be an
electroluminescent (EL) thin film light source.
[0032] FIG. 4 illustrates the light source 202 (FIG. 2A) according
to one embodiment. In one embodiment, the light source 202 is
composed of an organic light-emitting diode (OLED) 400 encapsulated
by a seal ring 402. The seal ring 402 can be formed of an adhesive,
epoxy, glue, or other suitable material. In the embodiment shown,
the seal ring 402 has a width of approximately 0.5 mm, and the
organic light-emitting diode (OLED) 400 is formed within the center
of the seal ring 402 having a width of substantially 1.0 mm. The
seal ring 402 can have a length that is substantially equivalent to
a length of an edge of a light guide plate. The seal ring 402 seals
the organic light-emitting diode (OLED) 400 between two substrates
as shown below with respect to FIG. 5. In one embodiment, the seal
ring 402 hermetically seals the organic light-emitting diode (OLED)
400 between the two substrates.
[0033] FIG. 5 illustrates a cross-sectional view of the light
source 202 along the line A-A of FIG. 4 according to one
embodiment. As shown in FIG. 5, the organic light-emitting diode
(OLED) 400 includes a (front) substrate 500, an anode 502, an
organic conductive layer 504 (commonly referred to as a "hole
injection layer" or "HIL"), an organic emissive layer 506, a
cathode 508 and a (back) substrate 510. The front substrate 500 can
be, for example, plastic, glass, or other suitable transparent
material. The back substrate 510 can be, e.g., glass, plastic, or
even a non-transparent material such as metal or foil. The anode
502 removes electrons (i.e., adds electron "holes") when a current
flows through the organic light-emitting diode (OLED). The
conductive layer 504 is made of organic plastic molecules that
transport "holes" from the anode 502. In one embodiment, a
conducting polymer used within the conductive layer 504 is
polyaniline. The organic emissive layer 506 is made of organic
plastic molecules (different from those within the conducting
layer) that transport electrons from the cathode 508. Light is made
in the organic emissive layer 506. In one embodiment, a polymer
used within the organic emissive layer 506 is polyfluorene. Other
suitable materials can be used. The front substrate 500 is
adhesively bonded to the back substrate 510 by the seal ring 402.
In one embodiment, the front substrate 500 is adhesively bonded to
an edge of a light guide plate as discussed in greater detail
below.
[0034] FIGS. 6-8 respectively illustrate various embodiments of a
front lighting system. Referring first to FIG. 6, a front lighting
system 600 is shown including a light source 602, a light guide
plate 604, and an angle-matching component 606. In one embodiment,
the light source 602 is bonded to an edge of a light guide plate
604, and the angle-matching component 606 is a feature of the light
guide plate 604--i.e., the angle-matching component 606 is molded
directly into the light guide plate 604. Alternatively, the
angle-matching component 606 can be separate from the light guide
plate 604. In one embodiment, the angle-matching component has a
substantially parabolic (or elliptical) shape for collimating the
light from the light source 602 (e.g., an organic light-emitting
diode (OLED)) into the edge of the light guide plate 604. Referring
to FIG. 7, a front lighting system 700 is shown including a light
source 702 bonded to a surface of a light guide plate 704. In this
embodiment, the light guide plate 704 includes a reflector 706 to
direct light from the light source 702 throughout the light guide
plate 704. In one embodiment, the reflector 706 is a compound
parabolic collector (CPC) or a sub-portion of a CPC. FIG. 8
illustrates a front lighting system 800 including a light source
802 and a tapered light guide plate 804 for uniformly directing
light onto a display device (not shown). In the embodiment of FIG.
8, the tapered light guide plate 804 has a tapered thickness along
a length of the light guide plate. The tapered light guide plate
804 can further include a plurality of facets molded onto a surface
(or a film laminate applied to the surface) for directing light
onto a display device. Although FIGS. 6-8 show separate embodiments
of a front light system, one or more of the features of the various
embodiments discussed with respect to FIG. 6-8 can be combined into
a single embodiment of a front light system.
[0035] As discussed above, the various embodiments of a front
lighting system described herein may be implemented in any device
that is configured to display an image, whether in motion (e.g.,
video) or stationary (e.g., still image), and whether textual or
pictorial. One particular type of display device--an
interferometric modulator display--that can implement the various
embodiments of a front lighting system will now be discussed.
[0036] Referring to FIG. 9, one interferometric modulator display
embodiment comprising an interferometric MEMS display element is
illustrated. In these devices, the pixels are in either a bright or
dark state. In the bright ("on" or "open") state, the display
element reflects a large portion of incident visible light to a
user. When in the dark ("off" or "closed") state, the display
element reflects little incident visible light to the user.
Depending on the embodiment, the light reflectance properties of
the "on" and "off" states may be reversed. MEMS pixels can be
configured to reflect predominantly at selected colors, allowing
for a color display in addition to black and white.
[0037] FIG. 9 is an isometric view depicting two adjacent pixels in
a series of pixels of a visual display, wherein each pixel
comprises a MEMS interferometric modulator. In some embodiments, an
interferometric modulator display comprises a row/column array of
these interferometric modulators. Each interferometric modulator
includes a pair of reflective layers positioned at a variable and
controllable distance from each other to form a resonant optical
gap with at least one variable dimension. In one embodiment, one of
the reflective layers may be moved between two positions. In the
first position, referred to herein as the relaxed position, the
movable reflective layer is positioned at a relatively large
distance from a fixed partially reflective layer. In the second
position, referred to herein as the actuated position, the movable
reflective layer is positioned more closely adjacent to the
partially reflective layer. Incident light that reflects from the
two layers interferes constructively or destructively depending on
the position of the movable reflective layer, producing either an
overall reflective or non-reflective state for each pixel.
[0038] The depicted portion of the pixel array in FIG. 9 includes
two adjacent interferometric modulators 12a and 12b. In the
interferometric modulator 12a on the left, a movable reflective
layer 14a is illustrated in a relaxed position at a predetermined
distance from an optical stack 16a, which includes a partially
reflective layer. In the interferometric modulator 12b on the
right, the movable reflective layer 14b is illustrated in an
actuated position adjacent to the optical stack 16b.
[0039] The optical stacks 16a and 16b (collectively referred to as
optical stack 16), as referenced herein, typically comprise of
several fused layers, which can include an electrode layer, such as
indium tin oxide (ITO), a partially reflective layer, such as
chromium, and a transparent dielectric. The optical stack 16 is
thus electrically conductive, partially transparent and partially
reflective, and may be fabricated, for example, by depositing one
or more of the above layers onto a transparent substrate 20. The
partially reflective layer can be formed from a variety of
materials that are partially reflective such as various metals,
semiconductors, and dielectrics. The partially reflective layer can
be formed of one or more layers of materials, and each of the
layers can be formed of a single material or a combination of
materials. In some embodiments, the layers of the optical stack are
patterned into parallel strips, and may form row electrodes in a
display device as described further below. The movable reflective
layers 14a, 14b may be formed as a series of parallel strips of a
deposited metal layer or layers (orthogonal to the row electrodes
of 16a, 16b) deposited on top of posts 18 and an intervening
sacrificial material deposited between the posts 18. When the
sacrificial material is etched away, the movable reflective layers
14a, 14b are separated from the optical stacks 16a, 16b by a
defined gap 19. A highly conductive and reflective material such as
aluminum may be used for the reflective layers 14, and these strips
may form column electrodes in a display device.
[0040] With no applied voltage, the gap 19 remains between the
movable reflective layer 14a and optical stack 16a, with the
movable reflective layer 14a in a mechanically relaxed state, as
illustrated by the pixel 12a in FIG. 1. However, when a potential
difference is applied to a selected row and column, the capacitor
formed at the intersection of the row and column electrodes at the
corresponding pixel becomes charged, and electrostatic forces pull
the electrodes together. If the voltage is high enough, the movable
reflective layer 14 is deformed and is forced against the optical
stack 16. A dielectric layer (not illustrated in this Figure)
within the optical stack 16 may prevent shorting and control the
separation distance between layers 14 and 16, as illustrated by
pixel 12b on the right in FIG. 9. The behavior is the same
regardless of the polarity of the applied potential difference. In
this way, row/column actuation that can control the reflective vs.
non-reflective pixel states is analogous in many ways to that used
in conventional LCD and other display technologies.
[0041] FIGS. 10-12 and 13A-13B illustrate one exemplary process and
system for using an array of interferometric modulators in a
display application.
[0042] FIG. 10 is a system block diagram illustrating one
embodiment of an electronic device that may incorporate aspects of
the invention. In the exemplary embodiment, the electronic device
includes a processor 21 which may be any general purpose single- or
multi-chip microprocessor such as an ARM, Pentium.RTM., Pentium
II.RTM., Pentium III.RTM., Pentium IV.RTM., Pentium.RTM. Pro, an
8051, a MIPS.RTM., a Power PC.RTM., an ALPHA.RTM., or any special
purpose microprocessor such as a digital signal processor,
microcontroller, or a programmable gate array. As is conventional
in the art, the processor 21 may be configured to execute one or
more software modules. In addition to executing an operating
system, the processor may be configured to execute one or more
software applications, including a web browser, a telephone
application, an email program, or any other software
application.
[0043] In one embodiment, the processor 21 is also configured to
communicate with an array driver 22. In one embodiment, the array
driver 22 includes a row driver circuit 24 and a column driver
circuit 26 that provide signals to a display array or panel 30. The
cross section of the array illustrated in FIG. 9 is shown by the
lines 1-1 in FIG. 10. For MEMS interferometric modulators, the
row/column actuation protocol may take advantage of a hysteresis
property of these devices illustrated in FIG. 11. It may require,
for example, a 10 volt potential difference to cause a movable
layer to deform from the relaxed state to the actuated state.
However, when the voltage is reduced from that value, the movable
layer maintains its state as the voltage drops back below 10 volts.
In the exemplary embodiment of FIG. 11, the movable layer does not
relax completely until the voltage drops below 2 volts. There is
thus a range of voltage, about 3 to 7 V in the example illustrated
in FIG. 11, where there exists a window of applied voltage within
which the device is stable in either the relaxed or actuated state.
This is referred to herein as the "hysteresis window" or "stability
window." For a display array having the hysteresis characteristics
of FIG. 11, the row/column actuation protocol can be designed such
that during row strobing, pixels in the strobed row that are to be
actuated are exposed to a voltage difference of about 10 volts, and
pixels that are to be relaxed are exposed to a voltage difference
of close to zero volts. After the strobe, the pixels are exposed to
a steady state voltage difference of about 5 volts such that they
remain in whatever state the row strobe put them in. After being
written, each pixel sees a potential difference within the
"stability window" of 3-7 volts in this example. This feature makes
the pixel design illustrated in FIG. 9 stable under the same
applied voltage conditions in either an actuated or relaxed
pre-existing state. Since each pixel of the interferometric
modulator, whether in the actuated or relaxed state, is essentially
a capacitor formed by the fixed and moving reflective layers, this
stable state can be held at a voltage within the hysteresis window
with almost no power dissipation. Essentially no current flows into
the pixel if the applied potential is fixed.
[0044] In typical applications, a display frame may be created by
asserting the set of column electrodes in accordance with the
desired set of actuated pixels in the first row. A row pulse is
then applied to the row 1 electrode, actuating the pixels
corresponding to the asserted column lines. The asserted set of
column electrodes is then changed to correspond to the desired set
of actuated pixels in the second row. A pulse is then applied to
the row 2 electrode, actuating the appropriate pixels in row 2 in
accordance with the asserted column electrodes. The row 1 pixels
are unaffected by the row 2 pulse, and remain in the state they
were set to during the row 1 pulse. This may be repeated for the
entire series of rows in a sequential fashion to produce the frame.
Generally, the frames are refreshed and/or updated with new display
data by continually repeating this process at some desired number
of frames per second. A wide variety of protocols for driving row
and column electrodes of pixel arrays to produce display frames are
also well known and may be used.
[0045] FIGS. 12 and 13A-13B illustrate one possible actuation
protocol for creating a display frame on the 3.times.3 array of
FIG. 10. FIG. 12 illustrates a possible set of column and row
voltage levels that may be used for pixels exhibiting the
hysteresis curves of FIG. 11. In the embodiment shown in FIG. 12,
actuating a pixel involves setting the appropriate column to
-V.sub.bias, and the appropriate row to +.DELTA.V, which may
correspond to -5 volts and +5 volts, respectively. Relaxing the
pixel is accomplished by setting the appropriate column to
+V.sub.bias, and the appropriate row to the same +.DELTA.V,
producing a zero volt potential difference across the pixel. In
those rows where the row voltage is held at zero volts, the pixels
are stable in whatever state they were originally in, regardless of
whether the column is at +V.sub.bias, or -V.sub.bias. As is also
illustrated in FIG. 12, it will be appreciated that voltages of
opposite polarity than those described above can be used, e.g.,
actuating a pixel can involve setting the appropriate column to
+V.sub.bias, and the appropriate row to -.DELTA.V. In this
embodiment, releasing the pixel is accomplished by setting the
appropriate column to -V.sub.bias, and the appropriate row to the
same -.DELTA.V, producing a zero volt potential difference across
the pixel.
[0046] FIG. 13B is a timing diagram showing a series of row and
column signals applied to the 3.times.3 array of FIG. 10 which will
result in the display arrangement illustrated in FIG. 13A, where
actuated pixels are non-reflective. Prior to writing the frame
illustrated in FIG. 13A, the pixels can be in any state, and in
this example, all the rows are at 0 volts, and all the columns are
at +5 volts. With these applied voltages, all pixels are stable in
their existing actuated or relaxed states.
[0047] In the FIG. 13A frame, pixels (1,1), (1,2), (2,2), (3,2) and
(3,3) are actuated. To accomplish this, during a "line time" for
row 1, columns 1 and 2 are set to -5 volts, and column 3 is set to
+5 volts. This does not change the state of any pixels, because all
the pixels remain in the 3-7 volt stability window. Row 1 is then
strobed with a pulse that goes from 0, up to 5 volts, and back to
zero. This actuates the (1,1) and (1,2) pixels and relaxes the
(1,3) pixel. No other pixels in the array are affected. To set row
2 as desired, column 2 is set to -5 volts, and columns 1 and 3 are
set to +5 volts. The same strobe applied to row 2 will then actuate
pixel (2,2) and relax pixels (2,1) and (2,3). Again, no other
pixels of the array are affected. Row 3 is similarly set by setting
columns 2 and 3 to -5 volts, and column 1 to +5 volts. The row 3
strobe sets the row 3 pixels as shown in FIG. 5A. After writing the
frame, the row potentials are zero, and the column potentials can
remain at either +5 or -5 volts, and the display is then stable in
the arrangement of FIG. 13A. It will be appreciated that the same
procedure can be employed for arrays of dozens or hundreds of rows
and columns. It will also be appreciated that the timing, sequence,
and levels of voltages used to perform row and column actuation can
be varied widely within the general principles outlined above, and
the above example is exemplary only, and any actuation voltage
method can be used with the systems and methods described
herein.
[0048] FIGS. 14A-14B are system block diagrams illustrating an
embodiment of a display device 40. The display device 40 can be,
for example, a cellular or mobile telephone. However, the same
components of display device 40 or slight variations thereof are
also illustrative of various types of display devices such as
televisions and portable media players.
[0049] The display device 40 includes a housing 41, a display 30,
an antenna 43, a speaker 44, an input device 48, and a microphone
46. The housing 41 is generally formed from any of a variety of
manufacturing processes as are well known to those of skill in the
art, including injection molding, and vacuum forming. In addition,
the housing 41 may be made from any of a variety of materials,
including but not limited to plastic, metal, glass, rubber, and
ceramic, or a combination thereof. In one embodiment the housing 41
includes removable portions (not shown) that may be interchanged
with other removable portions of different color, or containing
different logos, pictures, or symbols.
[0050] The display 30 of exemplary display device 40 may be any of
a variety of displays, including a bi-stable display, as described
herein. In other embodiments, the display 30 includes a flat-panel
display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described
above, or a non-flat-panel display, such as a CRT or other tube
device, as is well known to those of skill in the art. However, for
purposes of describing the present embodiment, the display 30
includes an interferometric modulator display, as described
herein.
[0051] The components of one embodiment of exemplary display device
40 are schematically illustrated in FIG. 14B. The illustrated
exemplary display device 40 includes a housing 41 and can include
additional components at least partially enclosed therein. For
example, in one embodiment, the exemplary display device 40
includes a network interface 27 that includes an antenna 43 which
is coupled to a transceiver 47. The transceiver 47 is connected to
a processor 21, which is connected to conditioning hardware 52. The
conditioning hardware 52 may be configured to condition a signal
(e.g. filter a signal). The conditioning hardware 52 is connected
to a speaker 45 and a microphone 46. The processor 21 is also
connected to an input device 48 and a driver controller 29. The
driver controller 29 is coupled to a frame buffer 28, and to an
array driver 22, which in turn is coupled to a display array 30. A
power supply 50 provides power to all components as required by the
particular exemplary display device 40 design.
[0052] The network interface 27 includes the antenna 43 and the
transceiver 47 so that the exemplary display device 40 can
communicate with one ore more devices over a network. In one
embodiment the network interface 27 may also have some processing
capabilities to relieve requirements of the processor 21. The
antenna 43 is any antenna known to those of skill in the art for
transmitting and receiving signals. In one embodiment, the antenna
transmits and receives RF signals according to the IEEE 802.11
standard, including IEEE 802.11(a), (b), or (g). In another
embodiment, the antenna transmits and receives RF signals according
to the BLUETOOTH standard. In the case of a cellular telephone, the
antenna is designed to receive CDMA, GSM, AMPS or other known
signals that are used to communicate within a wireless cell phone
network. The transceiver 47 pre-processes the signals received from
the antenna 43 so that they may be received by and further
manipulated by the processor 21. The transceiver 47 also processes
signals received from the processor 21 so that they may be
transmitted from the exemplary display device 40 via the antenna
43.
[0053] In an alternative embodiment, the transceiver 47 can be
replaced by a receiver. In yet another alternative embodiment,
network interface 27 can be replaced by an image source, which can
store or generate image data to be sent to the processor 21. For
example, the image source can be a digital video disc (DVD) or a
hard-disc drive that contains image data, or a software module that
generates image data.
[0054] Processor 21 generally controls the overall operation of the
exemplary display device 40. The processor 21 receives data, such
as compressed image data from the network interface 27 or an image
source, and processes the data into raw image data or into a format
that is readily processed into raw image data. The processor 21
then sends the processed data to the driver controller 29 or to
frame buffer 28 for storage. Raw data typically refers to the
information that identifies the image characteristics at each
location within an image. For example, such image characteristics
can include color, saturation, and gray-scale level.
[0055] In one embodiment, the processor 21 includes a
microcontroller, CPU, or logic unit to control operation of the
exemplary display device 40. Conditioning hardware 52 generally
includes amplifiers and filters for transmitting signals to the
speaker 45, and for receiving signals from the microphone 46.
Conditioning hardware 52 may be discrete components within the
exemplary display device 40, or may be incorporated within the
processor 21 or other components.
[0056] The driver controller 29 takes the raw image data generated
by the processor 21 either directly from the processor 21 or from
the frame buffer 28 and reformats the raw image data appropriately
for high speed transmission to the array driver 22. Specifically,
the driver controller 29 reformats the raw image data into a data
flow having a raster-like format, such that it has a time order
suitable for scanning across the display array 30. Then the driver
controller 29 sends the formatted information to the array driver
22. Although a driver controller 29, such as a LCD controller, is
often associated with the system processor 21 as a stand-alone
Integrated Circuit (IC), such controllers may be implemented in
many ways. They may be embedded in the processor 21 as hardware,
embedded in the processor 21 as software, or fully integrated in
hardware with the array driver 22.
[0057] Typically, the array driver 22 receives the formatted
information from the driver controller 29 and reformats the video
data into a parallel set of waveforms that are applied many times
per second to the hundreds and sometimes thousands of leads coming
from the display's x-y matrix of pixels.
[0058] In one embodiment, the driver controller 29, array driver
22, and display array 30 are appropriate for any of the types of
displays described herein. For example, in one embodiment, driver
controller 29 is a conventional display controller or a bi-stable
display controller (e.g., an interferometric modulator controller).
In another embodiment, array driver 22 is a conventional driver or
a bi-stable display driver (e.g., an interferometric modulator
display). In one embodiment, a driver controller 29 is integrated
with the array driver 22. Such an embodiment is common in highly
integrated systems such as cellular phones, watches, and other
small area displays. In yet another embodiment, display array 30 is
a typical display array or a bi-stable display array (e.g., a
display including an array of interferometric modulators).
[0059] The input device 48 allows a user to control the operation
of the exemplary display device 40. In one embodiment, input device
48 includes a keypad, such as a QWERTY keyboard or a telephone
keypad, a button, a switch, a touch-sensitive screen, a pressure-
or heat-sensitive membrane. In one embodiment, the microphone 46 is
an input device for the exemplary display device 40. When the
microphone 46 is used to input data to the device, voice commands
may be provided by a user for controlling operations of the
exemplary display device 40.
[0060] Power supply 50 can include a variety of energy storage
devices as are well known in the art. For example, in one
embodiment, power supply 50 is a rechargeable battery, such as a
nickel-cadmium battery or a lithium ion battery. In another
embodiment, power supply 50 is a renewable energy source, a
capacitor, or a solar cell, including a plastic solar cell, and
solar-cell paint. In another embodiment, power supply 50 is
configured to receive power from a wall outlet.
[0061] In some implementations control programmability resides, as
described above, in a driver controller which can be located in
several places in the electronic display system. In some cases
control programmability resides in the array driver 22. Those of
skill in the art will recognize that the above-described
optimization may be implemented in any number of hardware and/or
software components and in various configurations.
[0062] The details of the structure of interferometric modulators
that operate in accordance with the principles set forth above may
vary widely. For example, FIGS. 15A-15E illustrate five different
embodiments of the movable reflective layer 14 and its supporting
structures. FIG. 15A is a cross section of the embodiment of FIG.
9, where a strip of metal material 14 is deposited on orthogonally
extending supports 18. In FIG. 15B, the moveable reflective layer
14 is attached to supports at the corners only, on tethers 32. In
FIG. 15C, the moveable reflective layer 14 is suspended from a
deformable layer 34, which may comprise a flexible metal. The
deformable layer 34 connects, directly or indirectly, to the
substrate 20 around the perimeter of the deformable layer 34. These
connections are herein referred to as support posts. The embodiment
illustrated in FIG. 15D has support post plugs 42 upon which the
deformable layer 34 rests. The movable reflective layer 14 remains
suspended over the gap, as in FIGS. 15A-15C, but the deformable
layer 34 does not form the support posts by filling holes between
the deformable layer 34 and the optical stack 16. Rather, the
support posts are formed of a planarization material, which is used
to form support post plugs 42. The embodiment illustrated in FIG.
15E is based on the embodiment shown in FIG. 15D, but may also be
adapted to work with any of the embodiments illustrated in FIGS.
15A-15C as well as additional embodiments not shown. In the
embodiment shown in FIG. 15E, an extra layer of metal or other
conductive material has been used to form a bus structure 44. This
allows signal routing along the back of the interferometric
modulators, eliminating a number of electrodes that may otherwise
have had to be formed on the substrate 20.
[0063] In embodiments such as those shown in FIGS. 15A-15E, the
interferometric modulators function as direct-view devices, in
which images are viewed from the front side of the transparent
substrate 20, the side opposite to that upon which the modulator is
arranged. In these embodiments, the reflective layer 14 optically
shields the portions of the interferometric modulator on the side
of the reflective layer opposite the substrate 20, including the
deformable layer 34. This allows the shielded areas to be
configured and operated upon without negatively affecting the image
quality. Such shielding allows the bus structure 44 in FIG. 15E,
which provides the ability to separate the optical properties of
the modulator from the electromechanical properties of the
modulator, such as addressing and the movements that result from
that addressing. This separable modulator architecture allows the
structural design and materials used for the electromechanical
aspects and the optical aspects of the modulator to be selected and
to function independently of each other. Moreover, the embodiments
shown in FIGS. 15C-15E have additional benefits deriving from the
decoupling of the optical properties of the reflective layer 14
from its mechanical properties, which are carried out by the
deformable layer 34. This allows the structural design and
materials used for the reflective layer 14 to be optimized with
respect to the optical properties, and the structural design and
materials used for the deformable layer 34 to be optimized with
respect to desired mechanical properties.
[0064] Various implementations of a front lighting system for a
display device have been described. Nevertheless, one or ordinary
skill in the art will readily recognize that there that various
modifications may be made to the implementations, and any variation
would be within the spirit and scope of the present invention. For
example, the techniques discussed above to implement a front
lighting system can also be used to implement a back lighting
system. In general, a back lighting system can be implemented with
less technical restrictions relative to a front lighting system.
For example, a light guide plate associated with a back lighting
system can be painted with a pattern of white dots to scatter
light. The pattern of white dots generally obscures light from
passing through the light guide plate and, therefore, such a
technique would not be used in a front lighting system. Other
suitable techniques, e.g., use of films, for scattering light can
be implemented in a back lighting system.
* * * * *